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X-ORIGINAL-URL:http://diracmaterials.org
X-WR-CALDESC:Events for Dirac Materials
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TZID:"Europe/Stockholm"
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TZOFFSETFROM:+0100
TZOFFSETTO:+0200
TZNAME:CEST
DTSTART:20190331T010000
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TZOFFSETFROM:+0200
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DTSTART:20191027T010000
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DTSTART;TZID="Europe/Stockholm":20191008T103000
DTEND;TZID="Europe/Stockholm":20191008T120000
DTSTAMP:20260409T152050
CREATED:20191007T115850Z
LAST-MODIFIED:20191007T120321Z
UID:1399-1570530600-1570536000@diracmaterials.org
SUMMARY:[CMT Seminar] Joe Bailey - Spin wave dynamics in ultrathin yttriumiron garnet measured with x-ray microscopy
DESCRIPTION:Title: Spin wave dynamics in ultrathin yttriumiron garnet measured with x-ray microscopy \nSpeaker: Joe Bailey\, from the PSI (Switzerland) \nTime: 10:30-11am Fika / 11-12am Talk \nAbstract: Magnonics\, the study and development of devices utilising collective spin excitations\, is a rapidly growing field\, covering both fundamental topics (antiferromagnetism[1]\, quasiparticle condensates[2]) and technological applications (MRAM[3]\, spintronics[4]). Yttrium iron garnet (YIG) is a ferrimagnetic insulator with the lowest known magnon damping factor of any material [5]. This low damping leads to a prevalence of nonlinear effects and notably the room temperature Bose-Einstein condensation (BEC) of magnons first reported by Demokritov et al in 2006[6]\, and subject of a number of investigations since[7]-[10]. Ultrathin structures will be required for applications butremainlargelyunexplored. Here I report on the design\, fabrication and characterization of microwave devicesbased on such ultrathin structures(YIG thickness~100nm).The spin wavedynamics weremeasured using both Brillouin Light Scattering (BLS) and time resolved scanning transmission x-ray microscopy(TR-STXM)\, locked in phase with microwave stimulation of the devices.Anumber of milestonesare reached for our novel devices.First\, we have explicitly measuredthe spin wave dispersion in YIG[11]\, and demonstratedthe existence of the finite momentum minimum required for magnon BEC. Second\, the BLSdata demonstratethat the condensate exists in our samples. These results are a key development towards addingcondensate phenomena to the thin film magnonics toolbox. \n \n
URL:http://diracmaterials.org/calendar2/cmt-seminar-joe-bailey-spin-wave-dynamics-in-ultrathin-yttriumiron-garnet-measured-with-x-ray-microscopy/
LOCATION:NORDITA // South  (Meeting Room 112.006B)\, Roslagstullsbacken 23\, Stockholm\, 106 91\, Sweden
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BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20191008T150000
DTEND;TZID="Europe/Stockholm":20191008T160000
DTSTAMP:20260409T152050
CREATED:20191007T120227Z
LAST-MODIFIED:20191007T120304Z
UID:1402-1570546800-1570550400@diracmaterials.org
SUMMARY:Nobel Prize Announcement - Colloquium
DESCRIPTION:Details: TBA \nhttps://www.kva.se/en/pressrum \n
URL:http://diracmaterials.org/calendar2/nobel-prize-announcement-colloquium/
LOCATION:Oskar Klein Auditorium\, Albanova Campus
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BEGIN:VEVENT
DTSTART;TZID="Europe/Stockholm":20191008T161500
DTEND;TZID="Europe/Stockholm":20191008T170000
DTSTAMP:20260409T152050
CREATED:20190925T180612Z
LAST-MODIFIED:20191007T115925Z
UID:1368-1570551300-1570554000@diracmaterials.org
SUMMARY:[Group Meeting] Adrien Bouhon - Weyl Nodes with Non-Abelian Charges
DESCRIPTION:Abstract:\nWeyl points trapped within a C_2T-symmetric plane (C2 = 180 degrees rotation\, and T = time reversal) possess non-Abelian topological charges on top of their chirality. E.g. three-level systems realize the quaternion group. This picture requires to go beyond the modeling of a band structure as a Grassmannian (where a single spectral gap is specified). The non-Abelian nature of Weyl points implies new types of obstruction\, where\, for instance\, two Weyl points with opposite chiralities may not annihilate. Also\, the non-Abelian charges can be converted through the braiding of Weyl points in momentum space. \n \nI will review three different yet equivalent ways of computing the non-Abelian charges: (i) as a non-cyclic phase defined from the parallel transport of the Hamiltonian along a base loop\, (ii) as the Euler class of a two-band subspace over a patch bounded by the base loop\, and (iii) as the winding number of the Pfaffian of the Wilsonnian Hamiltonian – of the two-band subspace – as the base loop flows over the patch.  \n \n
URL:http://diracmaterials.org/calendar2/group-meeting-adrien-bouhon-weyl-nodes-with-non-abelian-charges/
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